Internet is decentralized in nature. Even if you tried to undo that, what's stopping anyone from bridging a non-CN/RU Intranet to CN/RU-Intranet.
More importantly: who is to decide that? Should now a US-based organization dictate who EU/JP/Africa can communicate with? Applying such decisions at such a low level will only result in the balkanization of the Internet.
And I totally agree with your approach, cost-reward of CN/RU links don't make sense for 99% of people. But blocking should *still* be optional (opt-in vs opt-out is another debate), becase for some (e.g. hardware, financial firms), the benefits of being able to communicate with China and Russia might outweigh the constant spam/attacks.
On a general note, why do people constantly try to impose their perspective on others? "This is bad for me/most, therefore should be banned for all."